1. Field of the Invention
The present invention relates to a cooling device that is adapted to cool a gas or a liquid flowing through a conduit. The cooling device can be utilized in a personnel cooling apparatus such as a rebreather or a body cooling suit. The cooling device is lightweight and has a high cooling density.
2. Description of Related Art
Cooling devices such as those used to cool breathable air and to cool the body of a user are known in the prior art. For example, breathing devices are often utilized to protect a user from unacceptable air conditions in the environment surrounding the user. Firemen and military personnel utilize such breathing devices in hostile environments and the breathing device is often incorporated into a hazardous materials (Haz-Mat) suit. The breathing device can be an open-loop breathing device that continuously provides air from a fresh air source or can be a closed-loop breathing device that recycles the gas expired by the user.
An open-loop breathing device includes a canister of oxygen for supplying fresh oxygen to the user and the expired gas from the user is vented to the atmosphere. A closed-loop system is smaller and has a reduced weight as compared to an open-loop system. A closed-loop system includes an oxygen canister, which is generally smaller that the canister used in an open-loop system, and also includes a carbon dioxide (CO2) absorber. The expired gas from the user is recirculated through the CO2 absorber and oxygen is added to the recirculated gas to form a breathable gas composition.
These breathing devices are often used in an uncomfortably hot atmosphere, such as when battling a fire, creating great discomfort for the user. Further, in a closed-loop system, the CO2 absorber generates heat during the absorption process and therefore the recycled gas becomes warmer over time. Therefore, the recycled air should be cooled to enhance the comfort of the user and, in severe cases, to prevent serious respiratory injury or even death.
U.S. Pat. No. 4,314,566 by Kiwak discloses a closed-loop breathing apparatus that includes a heat exchanger for cooling the breathing gas. A heat sink is located inside the oxygen tank and a heat pipe connects the heat sink to a heat exchange element located outside of the tank and in contact with the stream of recycled breathing gas. As the high-pressure oxygen tank is discharged, the tank cools and the heat exchange element thereby cools the recycled breathing gas.
U.S. Pat. No. 4,586,500 by Glynn discloses a closed-loop breathing apparatus wherein the breathing tube is passed through a reservoir of boiling liquid that is open to the atmosphere. The boiling liquid cools the recycled breathing gas.
U.S. Pat. No. 4,635,629 by Thorp et al. discloses a breathing apparatus including a CO2 absorber. The breathing apparatus incorporates an evaporative cooler unit wherein water evaporates from the surface of a fabric as the recycled breathing gas flows over the fabric.
U.S. Pat. No. 5,269,293 by Lxc3x6ser et al. discloses a cooling apparatus for cooling breathing gas in a closed-loop system that includes an oxygen tank and a CO2 absorber. A sorption cooling unit cools the breathing gas before inhalation by the user. The sorption cooling unit includes a plurality of storage tanks to hold water and includes a zeolite based desiccant for adsorption of evaporated water. Water evaporates from the storage tanks thereby cooling the breathing gas stream and the water vapor is adsorbed by the zeolite in a separate adsorbent container. The adsorbent container is subdivided into a plurality of sections to facilitate the removal of heat from the absorbent. A valve is also provided between the water storage tanks and the adsorbent container to enable the user to periodically open and shut the connection between the storage tank and the adsorbent container.
In addition to a breathing apparatus, cooling devices have also been utilized to provided cooling directly to the body of the user through a cooled body suit. Examples of such devices are illustrated in U.S. Pat. No. 6,105,382 by Reason and U.S. Pat. No. 5,263,336 by Kuramarohit.
U.S. Pat. No. 5,291,750 by Parrish et al. discloses a micro-climate heating/cooling device that can be used to heat or cool a vest worn by a user. The heating/cooling device includes an evaporative cooler having an evaporator and an adsorption bed with a control valve disposed between the evaporator and the adsorption bed. Liquid is circulated through the vest and to an evaporator heat exchanger to cool the liquid.
Despite the foregoing, there remains a need for a lightweight cooling device for cooling a gas flow or a liquid flow. It would be advantageous if such a device could provide a high degree of cooling over an extended period of time and the cooling rate could be independently controlled by the user.
According to one embodiment, the present invention is directed to a cooling device that is adapted to cool a medium flowing through a conduit. The medium can be a gas such as a breathing gas or a liquid such as water.
According to a preferred embodiment, the cooling device includes an evaporative chamber disposed adjacent to a conduit and separated therefrom by a sidewall. A refrigerant liquid is disposed in the evaporative chamber. An adsorptive chamber is connected to the evaporative chamber by a vapor passageway, wherein refrigerant liquid evaporates in the evaporative chamber under reduced pressure and extracts heat through the sidewall from a medium flowing through the conduit. The gas flow is advantageously cooled without restricting the flow of the medium through the conduit. This can be particularly important in a rebreather apparatus where the breathing gas should flow easily through the conduit to minimize stress on the user.
According to another preferred embodiment, the cooling device includes an evaporative chamber disposed in thermal communication with a conduit, a liquid reservoir, means for supplying a refrigerant liquid from the liquid reservoir to the evaporative chamber and an adsorptive chamber connected to an evaporative chamber by a vapor passageway. Refrigerant liquid evaporates in the evaporative chamber and extracts heat through the first sidewall from a medium flowing through the conduit. By providing a liquid reservoir that is separate from the evaporative chamber, the flow of refrigerant liquid can be controlled, such as by using a valve. The reservoir can also be attached and detached from the cooling device to provide fresh refrigerant liquid to the cooling device. In one embodiment, the liquid reservoir is a flexible pouch, such as a plastic pouch that collapses upon removal of the liquid and is readily disposable.
According to another preferred embodiment, the cooling device includes an evaporative chamber in thermal communication with a conduit, a refrigerant liquid disposed within the evaporative chamber and an adsorptive chamber connected to the evaporative chamber by a vapor passageway, wherein the cooling device has a cooling density of at least about 600 J/g. When calculating the cooling density herein, the mass is taken as the mass of refrigerant liquid plus the mass of desiccant. A cooling device having such a high cooling density advantageously provide as high degree of cooling over an extended period of time. According to one embodiment, the cooling density is even higher, such as at least about 800 J/g.
According to another embodiment of the present invention, a cooling device is provided that includes an evaporative chamber adapted to contain a refrigerant liquid, an adsorptive chamber including a desiccant and a vapor passageway adapted to provide refrigerant liquid vapor from the evaporative chamber to the adsorptive chamber upon evaporation of a refrigerant liquid. The adsorptive chamber includes active cooling means, wherein the active cooling means extracts heat from the desiccant upon adsorption of refrigerant liquid vapor by the desiccant. By cooling the desiccant, which rises in temperature due to the heat of adsorption, the desiccant is able to adsorb additional quantities of refrigerant liquid and therefore provide enhanced cooling. The active cooling means can include, for example, a separate sorption cooler.
These and other embodiments of the present invention will become apparent from the following description of the invention.